Plotting instrument



vPA'I'ENTBD JAN. '19, 1904;

N. G. DAVIDSON. PLOI'TING INSTRUMENT.

APPLVIOATION FILED 00:12.27, 1902.

N0 MODEL.

Tn: Nonms vains co. PNoTaUTMo.. wAsMmGYoN, n. c.

UNITED STATES Patented january 19, 1904.

PATENT OEEICE.

NELS GEORGE DAVIDSON, OF'ANACONDA, MONTANA.

PLoTTlNG INSTRUMENT.

SPECIFICATIONforming' part of Letters Patent No. 749,921, dated January 19, 1904.

Application filed 0ctober27, 1902. Serial No. 129,007. (No model.) I

To all whom t may 007000770.'

Be it known that I, NELs GEORGE DAVID- SON, a citizen of the United States, residingsity of prolile drawings and involved calculations now generally employed in laying out this class of work.

In the accompanying sheet of drawings there is illustrated the preferred embodimentof the invention, and the construction and operation thereofl is described in the following specification.

In said drawings, Figure 1 is a view in elevation of the instrument. Fig. 2 is a detail sectional view of the same, showing the construction of the pivot. Fig. 3 is also a detail sectional view showing a slightly -rnodifled form of pivot. grammatic views showing one manner of using .the instrument.

Similar numerals of reference designate corresponding parts in all the figures of the drawings.

The instrument, as shown, comprises two members or arms 10 and 11, `connected intermediate their ends by means of a pivot 12. This pivot may be in the form of a rivet, as shown in Fig. 2, or a headed and threaded shank may be employed, upon which a clamping thumb-nut 122L may be screwed. The two arms 10 and 11 are located in diferent planes of movement, and their inner edges are straight, each of said edges being provided with a scale, the starting-point of which is the center of the pivot. The center of this pivot, as will be noted by reference to Fig. 1, is in direct alinement with the inner edges of the arms. One end of the arm 10 isenlarged, as

Figs. 491,4", and 4c are dia-A shown, and is preferably in the form of a sector 13, said quadrant being provided with a plurality of scales disposed concentrically to the pivot 12. The scales are marked into degrees and Yfractions thereof, the inner running from Zero to one hundred and eighty degrees, the outer being marked from the edge to the center, or ninety degrees, as illustrated. The corresponding end of the arm 11 constitutes an indicator 14, whichv moves over the sectorscales, the straight edge of said indicator coacting with the same. This arrangement is obtained by having the sector located on the side of the pivot opposite the straight edge, which is provided with the scale.

The manner of using thevinstrument may probably be best explained las follows: For

one hundred and forty degrees and formed of' two pieces, as shown in Fig. 4, the arms of the instrument are first arranged at the desiredl angle, thus showing upon the sectorscale the difference between the same and one hundred and eighty degrees, or a half-circle. The number of degrees thusifound is divided by two, or the number of pieces to be employed in the elbow. The. result is twenty degrees, and the instrument is then set with. the arms at this angle, after which one'arm is placed alongside one blade of a square and the sixand-one-half-inch Amark thereon (representing the diameter of the pipe) located at the corner of said square. The point of intersectionof the inner edge of the other arm of the instrument and the outer edge of the other blade of the square will indicate the distance between the throat and the back of the pipe-section to be cut. This arrangement is clearly illustrated in Fig. 4b. The distance thus obtained is then laid out upon the pipe-blank, as shown Fig. 4, and the line of cutis obtained in a -manner well understood. This of course is an example of the simplest character, but it will serve to indicatethe usefulness of the instrument, and it will be evident to those skilled in the'art that computations of a much more involved nature can be readily made.

As the results obtained must be accurate, certain featuresv should be noted, all of which are important to the successful operation of the instrument. In the first place the pivot for the two members or arms must be alined with the inner or active edges of the same, and the scales located along said edges must have their starting-points at the center of the pivot. Furthermore, the sector-scales should be concentric to the pivot, and the indicator edge of the pointer should aline with the active edge of the arm. This construction affords a simple instrument by means of which angles for various purposes can be quickly and accurately plotted and the necessity of profile drawings thereby avoided.

From the foregoing it is thought that the construction, operation, and many advantages of the herein-described invention will be apparent to those skilled in the art without further description, and it will be understood that various changes. in the size, shape, proportion, and minor details of construction may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

As an article of manufacture, an instrument of the class described comprising a pair of flat members pivoted together between their ends and swinging side by side in different planes, said members having adjacent straight edges, one of which extends from end to end thereof, coacting scales arranged on said coaeting edges and extending from the pivot toward one end of the instrument, the portion of one arm surrounding the pivot being provided on one face with a sector-scale disposed .concentrically to the pivot and extending on opposite sides of the same, the other member being movable over said face and having its straight edge coacting with the scale thereof.

In testimony that I claim the foregoing as my own I have hereto affixed my signature in the presence of two witnesses.

NELS GEORGE DAVIDSON.

Witnesses E. L. KUNKEL, W. W. J AMEssoN. 

